Hi, we're here from curiosity.com to help you get smarter in just a few minutes.

I'm Cody Gough.

And I'm Ashley Hamer.

Today you learn about what the first cities looked like and why humans built them,

from archaeologist and author Monica L. Smith. We'll also answer a

listener question about what makes pedestrians run into each other.

Let's run into some curiosity. What did ancient cities look like and what made

humans start building them in the first

place? It's time to get some answers in the first of our three-part city Sundays

miniseries with Monica L Smith. She's an archaeologist and a professor in the Department of Anthropology at

UCLA and she's the author of a new book called Cities, The First 6,000 Years.

She's going to kick off our special series by explaining why 6,000 years specifically?

Well, you know, prior to about 6,000 years ago, there were no cities anywhere on the planet,

and now they are the settlement in which more than half of the

world's population resides. So what I wanted to do with this book is to take an

archaeological spin on the long history of human settlements and think about why it is that

cities came into existence given that there is such a compelling form for us today.

Well, why did is coming to existence?

Were you able to get to the bottom of it?

Sure, you know, for the first 100,000 years or so of human existence,

our natural environment was a village-like settlement where everybody knew everybody else.

And that seemed perfectly satisfactory for many tens of thousands of years, but as people started to come together into larger

...